Storm water filter arrangement

ABSTRACT

A filter apparatus for filtering gross pollution from storm water for fitment to storm water traps located at the entry and exit of storm water, underground and drainage systems. The apparatus includes a gross pollution filter basket located below the entry level of storm water into the trap so as to provide a bypass channel to allow a volume of storm water to pass through the trap. SA storm water bypass means is arranged to restrict entry of incoming storm water and gross pollution into the bypass channel while the combined pressure of storm water and gross pollution inside the trap is such that storm water can still pass through the filter basket. 
     The bypass means which acts like a one-way valve is also arranged to allow storm water and gross pollution to pass into the bypass channel when the combined pressure of storm water and gross pollution inside the trap is such that the storm water is restricted from passing through the filter basket.

This invention relates to storm water filtration and in particular tothe filtering of gross pollution from storm water at its entry or exitfrom the storm water, underground and drainage systems.

BACKGROUND

Water quality degradation is a problem of growing proportions. Onemeasure of water quality is the amount of gross pollution that iscarried from our roads and streets into our storm water system andeventually into the reservoirs that we rely on for potable water, ourrivers and ultimately the ocean.

Gross pollution in the main (90%) comprises organic matter likebranches, twigs, leaves, and soil, the remainder being nonorganic matterlike plastic containers, bags, wrappers; paper; cans; and cigarettebutts.

In metropolitan and township areas storm water catchment consists ofroad surfaces and the entry points for storm water into the undergroundportion of a storm water drainage system consists of one or more gullytraps located along the sides of the road surfaces. There existdifferent types of gullies, the side entry and the surface grate beingthe two most common.

Serious academic and practical studies of road surface, curb and channeldesign relating to road usage and safety are combined with gully trapconfiguration (eg depression, grate, deflector, etc) studies to providethe optimum means by which to trap storm water, and the inevitable grosspollution carried by it, and directed into the drains below the roadsurface.

Such traps are designed to operate effectively in a range of storm waterrun off conditions including low flow to very high flow which ideallycaptures 100% of the flow but otherwise minimises the bypass of waterand pollutants downstream of the trap.

Regardless though of the effectiveness of the traps, the problemidentified by the inventors was how to effectively filter the full rangeof flows of water and prevent the entry of gross pollution into theunderground storm water drainage systems without affecting theefficiency of the traps.

One approach to the solution of this problem is disclosed in U.S. Pat.No. 5,232,587 which describes the use of a two stage grate filterarrangement which in theory is meant to provide a path of leastresistance to the storm water just internal and slightly below theentrance to the trap by providing a multi aperture grate and beyond thata further grate with larger apertures located rearward and internal ofthe trap opening.

As gross pollution of a size unable to pass through the grates buildsup, the resistance to flow through the grates increases and it is soonfound that the efficiency of the trap diminishes as is evidenced by theincreasing amount of bypass flow. Eventually, the grates become coveredwith gross pollution and the trap is no longer useful. The volume ofgross pollutants needed to produce this effect is quite small since thegrates are located just below the road surface level which thereforenecessitates frequent cleaning to maintain trap efficiency.

Thus the invention is directed to overcoming the problems describedabove while also reducing the maintenance commitment.

BRIEF DESCRIPTION OF THE INVENTION

In a broad aspect of the invention a gross pollution filter apparatusfor placement within a trap arrangement used in a storm water drainagesystem comprises a filter basket located below the entry level of thestorm water into the trap arrangement, the basket being adapted toprevent gross pollution passing into the trap arrangement, and thebasket also being located so as to provide a bypass channel to allow avolume of storm water to pass through the trap arrangement, and a stormwater bypass being arranged to restrict entry of incoming storm waterand gross pollution into said bypass channel while the combined pressureof storm water and gross pollution inside the trap arrangement is suchthat storm water can pass through the filter basket but which is alsoarranged to allow storm water to pass into the bypass channel when thecombined pressure of storm water and gross pollution inside the traparrangement is such that the storm water is restricted from passingthrough the filter basket.

In a further aspect of the invention the trap arrangement comprises aside entry pit and the filter basket is located in the pit opposite theentry point of the storm water and the storm water bypass means islocated across the top of the bypass channel which is located betweenthe entry point of the storm water and the filter basket

In a yet further aspect of the invention the storm water bypass means isa one way valve means.

Specific embodiments of the invention will now be described in somefurther detail with reference to and as illustrated in the accompanyingdrawings. These embodiments are illustrative, and are not meant to berestrictive of the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a side cross-sectional view of a gross pollution filterapparatus according to the invention located in a side entry traparrangement;

FIG. 2 depicts a cross-sectional view of a gross pollution filterapparatus;

FIG. 3 depicts a perspective view of a side entry trap arrangement andgross pollution filter in place;

FIG. 4 depicts a storm water bypass means in the form of a pivotableflap shown in a closed (non-bypass) position;

FIG. 5 depicts a storm water bypass means in the form of a pivotableflap in an open (bypass) position;

FIG. 6 depicts a side cross-sectional view of a further embodiment of agross pollution filter apparatus according to the invention having asubstantially vertical storm water bypass means; and

FIG. 7 depicts a side view of a gross pollution filter apparatus.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Road surfaces collect or are the primary collection area for storm waterin townships and metropolitan areas. A plurality of storm water trapsare located along the sides of roadways so as to facilitate thecollection of storm water and the redirection of that storm water intounderground storm water drainage systems which also occasionally useabove ground water ways to communicate storm water to reservoirs and/orthe ocean.

There exist as described previously a variety of trap arrangements andfor the purposes of describing this embodiment of the invention a sideentry trap is used. It will be appreciated that the invention may bereadily adapted to various other trap types. An example of a side entrytrap is depicted in FIGS. 1 and 3.

FIG. 1 depicts a road surface 10 adjacent a trap arrangement 12typically constructed of concrete which is moulded off site andtransported for installation or poured into a suitable formwork in situ.The arrangement has a lid 14 which is typically constructed ofreinforced concrete. The upper surface of the lid is at footpath level.

Storm water exits the trap arrangement via a passageway 16 whichcommunicates storm water into the underground storm water drainagesystem.

The storm water road surface run off entry aperture 18 is located on theside of the trap arrangement hence the use of the term side entry pit todescribe this particular arrangement.

FIG. 1 depicts a side view of the entry aperture 18 and the maximumpossible volume of storm water that may enter the trap arrangement isdetermined not only by the depicted height but also the width of thetrap. A typical proportion of width to height is depicted in FIG. 3.

The gross pollution filter apparatus of this embodiment comprises afilter basket 20 located below and on the opposite side of the entryaperture 18. The filter basket is sized or arranged so that a bypasschannel 22 is provided. The bypass channel is sized so that the maximumpossible volume of storm water that may enter the pit is capable ofpassing down the channel 22 in the event that the filter basket 20 isfully occupied by gross pollution and unable to pass any incoming stormwater.

The filter basket can be made of any suitable material however forrobustness and longevity a stainless steel sheet having a plurality ofcircular apertures is preferable. The size and shape of the aperturesmay vary from trap to trap as the size and type of expected grosspollutants vary from trap site to trap site.

The basket is so called because it is used to collect gross pollution,however, it may be configured as a permanent fixture in the trap or itmay be made removable for ease of extraction of gross pollutants.Typically, the gross pollution is vacuumed up or removed by hand or withan implement via the entry aperture. Alternatively the lid 14 can beremoved and the gross pollution may be extracted through the top of thetrap.

It has been found that two monthly extractions of gross pollutants issufficient to maintain the efficiency of the trap arrangement fittedwith a gross pollution filter of the invention. Of course, this willvary dependent on the expected amount of gross pollution to be collectedwhich may require that in certain seasons the traps are emptied moreoften or following special events when man-made gross pollution levelsare high.

The gap between the bottom level 24 of the entry aperture and the top ofone side 26 of the filter basket 20 is bridged in this embodiment by abypass means 28. In a preferred embodiment of the bypass means a flatplate 30 lies substantially in the plane of the storm water when itflows from the road surface into the trap. The absence of apertures inthe bypass means assists in preventing the movable action of the bypassmeans from being obstructed or hindered by gross pollutants.

The flat plate 30 is hinged along its width so as to be rotatablymovable downwards and in the arrangement depicted in FIGS. 1 to 3 to lieadjacent the internal wall of the trap 12 and thereby allow storm waterto access the bypass channel 22 from the filter basket side of thebypass means.

An elastomeric element 32, such as for example a spring, is anchored(not shown) at end 34 and attached to the flat plate 30 at 36, so as tobias the plate into a closed position so as not to allow access of stormwater into the bypass channel until sufficient pressure builds up toovercome the bias force of the spring. A stop (not shown) restrainsrotation of the plate towards the anchored end of the spring and islocated so as to position the plate substantially in the plane of stormwater flow between the entry aperture and the filter basket.

An embodiment of a bypass means is provided in greater detail in FIGS. 4and 5.

FIG. 2 depicts in greater detail an embodiment of the filter basket 22comprising a stainless steel sheet 38 having a plurality of circularapertures therein (not shown). The sheet is adapted to rest upon asupport member 40 and affixed thereto by fixing means, for example a pin42, which stops the sheet sliding off the member but is arranged so thatthe pin can be extracted from a complementary set of apertures in thesheet and support member so that the basket can be taken from the trapfor emptying.

The support member 40 is fixed to the side of the trap as depicted inFIGS. 1 and 3, by fixing means 42, for example a dyna-bolt.

The opposite side of the basket 20 is supported by a second supportmember 44 which, as does support member 40, extends the width of thetrap. The sheet 38 is adapted to rest upon the support member 44 and isfixed thereto by bracket 46.

The depth of the basket into the trap is determined largely by theamount of gross pollutants which are desired to be trapped. As depictedin FIG. 1, the basket is approximately two thirds of the depth of thetrap below the road surface level. Conveniently the bottom of the basketis approximately level with the top of the exit aperture of the traparrangement.

An additional shape supporting bar 48 is located approximately threefifths down the side of the basket adjacent the bypass channel and heldat this location by bar 50 which depends from support member 44. Thisarrangement reduces the deformation of the filter basket into the bypasschannel as gross pollution accumulates in the filter basket.

FIG. 3 depicts a perspective view of an in situ entry trap arrangementwith a gross pollution filter according to the invention.

FIG. 4 depicts a perspective view of an embodiment of a bypass means 28comprising a flat plate 30 and a hinge member 52 which may be preferablya nylon tape which is rugged enough to maintain an adequate hingefunction in the harsh environmental conditions of its use. Anelastomeric element 32 is provided in this embodiment by a spring fixedat one end to the flat plate 30 and at its other end to a frameworkmember 54 which itself is attached adjacent to the entry aperture 18 ofthe trap arrangement.

The spring biases the flat plate upwards and against stop 36 which inthis embodiment is formed by a triangular shaped sheet of metalprojecting from the framework member 54.

The bypass means depicted in FIGS. 1 to 5 is of the form describedabove, however, it is possible for a unitary sheet of plastic having amemory characteristic of its preferred shape to provide a functionallysimilar arrangement. Such an arrangement is provided by any form of oneway valve which closes off the entry to the bypass channel while thefilter basket is adequately passing storm water but which opens to allowexcess storm water to enter the bypass channel as required.

FIG. 4 depicts the bypass means in a closed position and FIG. 5 depictsa bypass means in an open position. Like elements in the foregoing Figsare identified with like numerals.

FIG. 6 depicts a side cross-sectional view of a top entry trap having agrating 58 located at the entry level and aperture of the trap. In mostarrangements the grating will act as a primary filter to grosspollutants which results in only a certain size of pollutants beingcarried into the trap. A diverter member 60 is located under a portionof the grate to direct storm water and any water borne pollutants intothe filter basket.

The bypass channel 22 is preferably sized so as to communicate themaximum or a reasonable proportion of the expected volume of storm watercollected by the trap.

In this embodiment the bypass means 28 has a vertical orientation andoperates in the same manner as that described previously. The flat plate30 of the bypass means 28 is biased in a closed position until thepressure of storm water on the filter basket side of the bypass means issufficient to overcome the bias force. The pressure of the storm watermoves the flat plate and allows the flow of storm water into the bypasschannel 22.

FIG. 7 depicts like elements of FIG. 6 with like numerals and the dottedoutline 30' shows the flat plate in a position to allow overflow ofstorm water into the bypass channel 22.

The two types of traps described in the specification are merelyexamples of traps to which the filter apparatus of this invention may beadapted. However, the filter apparatus can be made to suit many othertypes of traps.

It will be appreciated by those skilled in the art, that the inventionis not restricted in its use to the particular application described,nor is it restricted to the feature of the preferred embodimentsdescribed herein. It will be appreciated that various modifications canbe made without departing from the principles of the invention,therefore, the invention should be understood to include all suchmodifications within its scope.

We claim:
 1. A gross pollution filter apparatus for placement within atrap arrangement used in a storm water drainage system comprising:afilter basket located below the entry level of the storm water traparrangement, said basket being adapted to prevent gross pollutionpassing through said trap arrangement, said basket also being located soas to provide a bypass channel to allow a volume of storm water andgross pollution to pass through said trap arrangement; and a storm waterbypass means arranged to restrict entry of incoming storm water andgross pollution into said bypass channel while the combined pressure ofstorm water and gross pollution inside said trap arrangement is suchthat storm water can pass through said filter basket but which is alsoarranged to allow storm water and gross pollution to pass into saidbypass channel when the combined pressure of storm water and grosspollution inside said trap arrangement is such that said storm water isrestricted from passing through said filter basket.
 2. A gross pollutionfilter apparatus according to claim 1 wherein said storm water bypassmeans is a one-way valve means.
 3. A gross pollution filter apparatusaccording to claim 1 wherein said water bypass means is a biasedpivotable flap member and a stop, said stop positioned to restrict themovement of said flap member.
 4. A gross pollution filter apparatusaccording to claim 1 wherein said filter basket is removable.
 5. A grosspollution filter apparatus according to claim 1 wherein said filterbasket comprises a unitary sheet material having a plurality ofapertures therein and shaped so as to fit across an internal portion ofsaid trap arrangement.
 6. A gross pollution filter apparatus accordingto claim 5 wherein said sheet material is supported at is upper ends bybar members located across the internal width of said trap arrangement.7. A gross pollution filter apparatus according to claim 6 wherein saidsheet material is supported on at least one side intermediate its upperand lower extremities by support means to reduce the deformation of saidfilter basket into said bypass channel.
 8. A gross pollution filterapparatus according to claim 1 wherein said trap arrangement comprises aside entry pit and said filter basket is located in said pit oppositethe entry point of storm water and said storm water bypass means islocated across said bypass channel which lies between said entry pointof storm water and said filter basket.